This invention relates generally to devices which separate a gas and a liquid. The apparatus is particularly useful in separating air from oil. This is particularly useful in lubricating systems for gas turbine engines. Such systems are also applicable to transmission systems in general, and aircraft power transmissions in particular. Gas separators of this type may be combined with particle detection systems which monitor the metal particles which are normally and constantly being added to the oil during the course of normal use. Such systems are adapted to detect an increase in the quantity of such particles and to monitor the size of such particles, as an increase in either quantity or size may be indicative of an incipient structural failure.
Wear particles are generally two to twenty microns in size. Particles of this size, when suspended in a circulating fluid such as heavy lubricating oil, generally move with it rather than reacting promptly to gravitational and inertial forces. The quantity of such particles is normally relatively low and are readily removed from the system through the use of suitable filters, or by strategically placed magnets if the particles are magnetic.
When the components of the system which is being lubricated become overloaded or when localized areas of weaknesses occur, the situation changes radically. In such cases, much larger particles, or failure particles, of material become loosened generally at the point of contact between moving parts under high surface pressure. Once the surface has been deformed by the breaking off of such particles, the rate of deterioration accelerates, resulting in the breaking off of additional particles at increasing rates. Thus, the quantities of the wear particles produced are substantially increased. The larger or failure particles are also generated at ever increasing sizes. Failure particles generally fall into the one hundred to two thousand micron size range. Due to their greater mass, they are less subject to being suspended in the lubricating fluid and are forced outward by the centrifugal forces generated by a cyclonic debris separator.
Engine lubricating systems and transmission systems churn their fluids, causing them to be mixed with air, causing formations of foam which are often highly stable. In many systems, equal amounts of air, by volume, are mixed with the oil. In still other high speed applications such as the lubrication systems for gas turbines, as many as four parts of air may be mixed with one part of oil, by volume. Such dilution of the oil is obviously undesirable since it results in less oil coming in contact with the surfaces requiring lubrication, thus diminishing the lubricating effect of the oil. The presence of air in the oil results in the air being compressed, thus lowering the overall system pressure. This is particularly true when displacement type pumps are used, as is common in these types of systems.
Additionally, the cooling effect of the oil is substantially reduced by such entrapped air. This, of course, increases the probabilities of overheating and accelerated wear.
Cyclonic debris separators have been combined with filters for removing wear particles. Such a device is disclosed in U.S. Pat. No. 4,199,443, issued to Thomas E. Tauber on Apr. 22, 1980.
Cyclonic separators for removing entrapped air from oil are well known in the prior art. One such device is disclosed in U.S. Pat. No. 4,282,016, issued Aug. 4, 1981 to Thomas E. Tauber, et al, entitled "Gas and Failure Particle Separator System". This invention discloses a separator system combined with a particle detector wherein the oil and air enter through the top of the device, as does the separated air, while the oil exits from the bottom of the device.
Separators for removing air from oil necessarily require three inlets or outlets. One inlet is required for the oil with the entrapped air. One outlet is required for the air subsequent to its removal, and another outlet is required for the oil. The prior art devices have had inlets and outlets at both ends of the separator. This has caused problems in installing the apparatus where there are space limitations. Such space limitations are common in an aircraft environment.
It has been recognized in the prior art that it is desirable to combine devices having single functions to obtain a device having multiple functions. Oil filters have been provided to remove wear particles, particle separators have been provided to aid in the detection of failure particles, and air separators have been provided to remove entrapped air from oil. U.S. Pat. No. 4,199,443 to Tauber teaches the combining of a filter for wear particles with a cyclonic debris separator for aiding in the detection of failure particles; while U.S. Pat. No. 4,282,016 to Tauber, et al teaches the use of a cyclonic debris separator to separate air from oil, as well as aiding in the collection and detection of failure particles.